Current water soluble contrast materials are of low toxicity but have several disadvatages associated with their use. Adverse effects have been described to the high osmolality, alteration of ionic balances and protein binding of these water-soluble agents. We are proposing that a particulate contrast material should overcome the primary disadvantages of water-soluble contrast agents since particulate contrast materials are non-ionic and are not osmotically active regardless of suspension density. The objective of this proposal is to design and synthesize new particulate contrast media; design of these new agents will be guided by the results of a thorough evaluation of a particulate contrast material, iothalamate ethyl ester (IEE), previously developed in our laboratory. The approach proposed for this project involves: first, a thorough evaluation of the pharmacokinetics and protein binding of IEE particles to improve our understanding of the important phenomena occurring upon introduction of foreign particles into blood & lymph; and, second, to utilize this knowledge to design and synthesize new particulate contrast material with specific characteristics for use in angiography, hepatic CT and lymphography. All new particulate contrast material developed on this project will be evaluated for efficacy and toxicity.